Showing posts with label ANATOMY. Show all posts
Showing posts with label ANATOMY. Show all posts

ANATOMY OF SALIVARY GLANDS







The parotid gland

This is the largest of the salivary glands,
lying wedged between the mandible and sternocleidomastoid and overflowing both these bounding structures.

The parotid and its surrounds in a schematic horizontal section—the facial nerve is the most superficial of the structures traversing the gland.
Relations

Above—lie the external auditory meatus and temporomandibular joint.
Below—it overflows the posterior belly of digastric.
Anteriorly—it overflows the mandible with the overlying masseter.
Medially —lies the styloid process and its muscles separating the parotid from the internal jugular vein, internal carotid artery, last four cranial nerves and the lateral wall of the pharynx.
The gland itself is enclosed in a split in the investing fascia, lying both on and below which are the parotid lymph nodes.
Antero-inferiorly, this parotid fascia is thickened and is the only structure separating the parotid from the submandibular gland (the stylomandibular ligament).

Traversing the gland (from without in) are
1. the facial nerve;
2. the retromandibular (posterior facial) vein, formed by the junction of the superficial temporal and maxillary veins.
3. the external carotid artery, dividing at the neck of the mandible into its superficial temporal and maxillary terminal branches

The parotid duct (of Stensen)
The parotid duct (of Stensen) is 2in (5cm) long.
It arises from the anterior part of the gland,
runs over the masseters a finger’s breadth below the zygomatic arch to pierce the buccinator and
open opposite the second upper molar tooth.
The duct can easily be felt by a finger rolled over the masseter if this muscle is tensedby clenching the teeth.

THE RELATIONS OF THE FACIAL NERVE TO THE PAROTID

• The facial nerve is unique in traversing the substance of a gland, a fact of considerable importance .
• This coexistence is explained embryologically; the parotid gland develops in the crotch formed by the two major branches of the facial nerve.
• As the gland enlarges it overlaps these nerve trunks, the superficial and deep parts fuse and the nerve comes to lie buried within the gland.
• The facial nerve emerges from the stylomastoid foramen, winds laterally to the styloid process and can then be exposed in the inverted V between the bony part of the external auditory meatus and the mastoid process.
• This has a useful surface marking, the intertragic notch of the ear, which is situated directly over the facial nerve.
• Just beyond this point the nerve dives into the posterior aspect of the parotid gland and bifurcates  almost immediately into its two main divisions (occasionally it divides before entering the gland).
• The upper division divides into temporal and zygomatic branches;
• the lower division gives the buccal, mandibular and cervical branches.
• These two divisions may remain completely separate within the parotid, may form a plexus of intermingling connections,
• The branches of the nerve then emerge on the anterior aspect of the parotid to lie on the masseter, thence to pass to the muscles of the face.
• No branches emerge from the superficial aspect of the gland,

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Anatomy of the Bones of Cervical Spine

Anatomy of the Bones of Cervical Spine
Atlas
1st Cervical Vertabrae
 
Lack of Body
 
Superior Articular Foveae
Inferior Articulating Foveae
      Fovea Dentis 

Axis
C2

Dens-Rotation between skull and atlas
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Muscles of the Facial Expression


Muscles of the Facial Expression

Muscles of Facial Expression are unique in that they migrate to their destinations about the scalp, neck, and mostly about the face from second pharyngeal arch mesenchyme and thus receive their motor innervation via the facial nerve (CN VII), the nerve of the second arch. Although most of these muscles originate on bone, most do not insert on bone; rather, they insert into the dermis of the skin and freely intermingle with muscles in their vicinity. Upon contraction, this arrangement and groupings of muscles about the orifices of the face convey movements about these orifices that we interpret as emotions.
The muscles of the face (and scalp) are derived from the second pharyngeal arch (hyoid arch) mesenchyme that migrates to its final destination.
Muscles of the Face and Scalp
Considering the origin of these muscles, it is not surprising that they receive motor innervation from branches of the facial nerve (CN VII).
Rather than inserting into bone, these muscles insert into the dermis of the skin, thus their orchestrated contractions convey various shapes to the face that we interpret as emotions. It is important to understand that fascicles of these muscles intermingle with each other, and they tend to act in groups to control the orifices around which they are grouped, such as the orbit, nose, and mouth. It is according to this grouping that they are described.

Muscles of the Face and Scalp
Muscle
LocationOrigin
Scalp
FrontalisForeheadProcerus, corrugator, orbicularis oculi
OccipitalisBack of the headMastoid process and superior nuchal line
TemporoparietalisTempleTemporal fascia
Ear
Auricularis anteriorAnterior to earTemporal fascia
Auricularis superiorAbove earTemporal fascia
Auricularis posteriorBehind earMastoid process
Nose
Procerus


Nasalis


Depressor septi


Eye
Orbicularis oculiAround the orbitNasal process of frontal bone, frontal process of maxilla, medial palpebral ligament, and lacrimal bone
CorrugatorDeep to the orbicularis oculiMedial aspect of superciliary arch
Mouth
Levator labii superiorisUpper lipZygoma and maxilla just above infraorbital foramen
Levator labii superioris alaque nasiUpper lip and side of noseMaxilla, frontal process
Levator anguli orisCorner of mouthCanine fossa of maxilla
Zygomaticus majorCheek and corner of mouthTemporal process of zygoma
Zygomaticus minorCheek and corner of mouthMaxillary process of zygoma
RisoriusCheekMasseteric fascia
Depressor labii inferiorisLower lipOblique line of mandible
Depressor anguli orisCorner of mouthOblique line of mandible
MentalisChinIncisive fossa of mandible
Orbicularis orisCircumscribes the mouthMuscles in the vicinity, maxilla, nasal septum, mandible
BuccinatorCheekPterygomandibular raphe, alveola arches of mandible and maxilla
Neck
PlatysmaNeck and chinPectoral and deltoid fascia


Muscles of the Ear and Nose
The three external muscles of the ear are the auricularis anterior, superior, and posterior. Similarly, the three muscles of the nose are the procerus, nasalis, and depressor septi. These two groups of muscles are fairly inconsequential.

Muscles Surrounding the Orbit
Orbicularis Oculi
The orbicularis oculi muscle is composed of two parts, the palpebral portion and the orbital portion. The former originates from the medial palpebral ligament (attached to the medial aspect of the orbit) and inserts into the lateral palpebral raphe (attached to the lateral aspect of the orbit). The orbital portion of the muscle describes an oval around the orbit.
The orbicularis oculi is innervated by the temporal and zygomatic branches of the facial nerve and acts to close the eyelid completely. Forceful closure is mediated by the orbital portion, whereas the palpebral portion is responsible for light closure, as in blinking.

Corrugator
The corrugator (supercilii) muscle is located deep to the superomedial aspect of the orbicularis oculi, at the medial aspect of the eyebrow. It originates at the medial extent of the superciliary arch and inserts into the skin of the eyebrow.
It is innervated by the temporal and zygomatic branches of the facial nerve; the combined actions of the paired muscles approximate the eyebrows, producing frowns.

Muscles Surrounding the Mouth
Orbicularis Oris
The orbicularis oris completely encircles the mouth. Its fibers are positioned at various depths and angles in the two lips. Fascicles of this muscle, some of which are derived from those of neighboring muscles—especially the buccinator—freely intermingle with fascicles of other muscles acting on the lips, permitting extensive movability. Many of the fibers of the buccinator cross over each other at the angle of the mouth so the upper fibers proceed to the lower lip and the lower fibers to the upper lip. Hence, the origin of the orbicularis oris is complex and is usually considered to be from the fibers of the surrounding muscles as well as from the alveolar portion of the maxilla, the septum of the nose, and the area lateral to the incisive fossa of the mandible. Insertion is into the skin and into itself, forming an ellipse around the mouth.
Buccal branches of the facial nerve innervate this complex muscle, which closes the lips and, during stronger contraction, purses them, as in osculation and whistling.

Risorius
The risorius is a small, horizontally placed muscle that originates in the masseteric fascia and inserts in the skin of the corner of the mouth. This is the smiling muscle; it is responsible for drawing the corners of the mouth laterally. The risorius is innervated by buccal and mandibular branches of the facial nerve.

Depressors of the Lip
The depressor labii inferioris is quadrangular in shape. It originates on the medial extent of the oblique line of the mandible and inserts into the skin of the lower lip. It acts to depress the lower lip.
The depressor anguli oris (triangularis) originates on the oblique line of the mandible and inserts into the skin of the corner of the mouth and depresses it, expressing sadness.
The mentalis is a small muscle of the chin. Its origin is in the incisive fossa of the mandible, and it inserts into the skin of the chin to wrinkle it and also to protrude the lower lip, as in drinking.
The platysma was previously detailed in Chapter 7. All of the muscles of this group, except the platysma, are innervated by the buccal and mandibular branches of the facial nerve.

Elevators of the Lip
Five muscles elevate the lip and corner of the mouth. The levator labii superioris alaque nasi is the most medial of these muscles, originating from the frontal process of the maxilla passing inferiorly along the side of the nose. It then splits into a medial and a lateral portion to insert into the wing of the nose and into the upper lip. This muscle functions in dilating the nostril and raising the upper lip.
The levator labii superioris originates from the maxilla and zygoma just inferior to the orbit. Its fibers pass across the infraorbital foramen to insert into the upper lip, lateral to and intermingling with the fibers of the levator labii superioris alaque nasi. The levator labii superioris elevates and protrudes the upper lip.
The levator anguli oris lies deep to the levator labii superioris. It originates below the infraorbital foramen, from the canine fossa of the maxilla, to insert into the corner of the mouth. This muscle elevates the angle of the mouth and assists in the formation of the nasolabial furrow.
The zygomaticus minor, a slender muscle arising from the maxillary process of the zygomatic bone, inserts just lateral to the insertion of the levator labii superioris muscle. This muscle elevates the upper lip. It also assists in the formation of the nasolabial furrow.
The zygomaticus major is the lateral-most muscle of this group. It originates on the temporal process of the zygomatic bone and inserts into the corner of the mouth. This muscle elevates the corner of the mouth and pulls it laterally.
All of the five muscles acting to elevate the lips are innervated by the buccal branches of the facial nerve.

Muscle of the Cheek
The buccinator, a quadrangule-shaped muscle occupying the space between the mandible and the maxilla, is the primary muscular component of the cheek. It lies deep to the muscles of facial expression and is separated from them by the buccopharyngeal facia and the buccal fat pad. The parotid duct pierces the substance of this muscle to enter the oral vestibule.
The buccinator originates on the maxilla and mandible, specifically on the buccal surfaces of the alveolar processes in the vicinity of the three molars, and from the pterygomandibular raphe, a collagenous tendinous inscription attached to the pterygoid hamulus and the mylohyoid line of the mandible. This raphe is interposed between the buccinator and superior pharyngeal constrictor muscles.
The buccinator inserts into the fleshy corner of the lip in such a fashion that the upper fascicles and the lower fascicles decussate at the corner of the mouth and insert into the lower and upper lips, respectively, becoming fibers of the orbicularis oris. The highest and lowest fascicles, however, continue without decussation into the upper and lower lips, respectively.
The buccinator muscle acts to press the mucosa of the cheek against the teeth, thus aiding in mastication and deglutition. In addition, it assists in distending the oral vestibule and forcefully expelling air, as in blowing dust particles off a surface. The buccal branch of the facial nerve innervates this muscle.

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PTERYGOPALATINE FOSSA

PTERYGOPALATINE FOSSA

The pterygopalatine fossa—
           A small, pyramid-shaped space.
           Situated between the maxilla, sphenoid, and palatine bones.
           It communicates via canals, fissures, and foramina with various regions of the skull.
          The contents of the pterygopalatine fossa include
                     The terminal portion of the maxillary artery;
                     The pterygopalatine ganglion;
                     The maxillary division of the trigeminal nerve; and branches of these structures.
Maxillary Artery
The third, or pterygopalatine portion, of the maxillary artery enters the pterygopalatine fossa from the infratemporal fossa via the pterygomaxillary fissure
Maxillary artery and its distribution in the deep face

Branches of the pterygopalatine portion of the maxillary artery are the posterosuperior alveolar, infraorbital, greater palatine, pharyngeal, and sphenopalatine arteries as well as the artery of the pterygoid canal.
The posterior superior alveolar artery branches from the maxillary artery as that vessel enters the pterygomaxillary fissure. It travels on the maxillary tuberosity and enters the posterior superior alveolar foramen accompanied by the like-named nerve. The vessel ramifies within the maxilla to vascularize the maxillary sinus, molars, and premolars as well as the neighboring gingiva.
The infraorbital artery, a continuation of the maxillary artery, enters the orbit through the inferior orbital fissure, lies in the infraorbital groove, leaves the orbit via the infraorbital canal, and enters the face by way of the infraorbital foramen. Branches of the infraorbital artery are the orbital branches, serving the lacrimal gland and the inferior oblique and inferior rectus muscles; the anterior superior alveolar branches, which vascularize the anterior teeth and the maxillary sinus; and the facial branches.
The greater palatine artery and its branch, the lesser palatine artery, pass through the pterygopalatine canal and gain entrance to the palate via the greater palatine and lesser palatine foramina, respectively, to vascularize the hard and soft palates as well as associated structures. The pharyngeal branch passes dorsally, through the pharyngeal canal, to vascularize the auditory tube, sphenoidal sinus, and portions of the pharynx. The sphenopalatine artery leaves the pterygopalatine fossa via the sphenopalatine foramen on its medial wall to enter the nasal fossa. The distribution of this vessel and its branches is discussed later in this chapter. The small artery of the pterygoid canal passes through the posterior wall of the pterygopalatine fossa via the pterygoid canal. It supplies part of the auditory tube, pharynx, middle ear, and sphenoidal sinus.
Maxillary Nerve

The maxillary division of the trigeminal nerve enters the pterygopalatine fossa at its posterior boundary via the foramen rotundum. While in the fossa, it gives off the zygomatic nerve, which, passing into the orbit through the inferior orbital fissure, will bifurcate to form the zygomaticotemporal and zygomaticofacial nerves.
The maxillary division of the trigeminal nerve
The posterior superior alveolar nerves also branch from the maxillary nerve, exit the fossa via the pterygomaxillary fissure, and enter the maxillary tuberosity to serve the maxillary sinus, molars, and adjacent gingiva and cheek. The maxillary nerve then enters the orbit by way of the inferior orbital fissure and is referred to as the infraorbital nerve.
While in the pterygopalatine fossa, the maxillary nerve communicates with the pterygopalatine ganglion via two small trunks, the pterygopalatine nerves; however, these nerves do not bear a functional relationship with the ganglion. Postganglionic parasympathetic fibers derived from the ganglion ride along and distribute with branches of the maxillary division of the trigeminal nerve.
Pterygopalatine ganglion and associated nerves and arteries
Orbital branches are slender nerves that supply the periosteum of the orbit and the mucoperiosteum of the ethmoidal and sphenoidal sinuses. The greater palatine nerve and its branches, the lesser palatine and posterior inferior nasal branches, descend through the pterygopalatine canal to supply regions of the palate, gingiva, tonsil, and lateral wall of the nasal fossa.
Posterior superior nasal branches leave the pterygopalatine fossa via the sphenopalatine foramen to serve the posterior aspect of the nasal fossa and part of the ethmoidal sinus. Its nasopalatine branch grooves the vomer bone in its path to the incisive foramen of the anterior hard palate, which it supplies. The pharyngeal nerve traverses the pharyngeal canal to innervate part of the nasopharynx.

Pterygopalatine Ganglion
The pterygopalatine ganglion seems to be functionally associated with the maxillary division of the trigeminal nerve because it is suspended by the pterygopalatine nerves within the fossa. It is, however, a parasympathetic ganglion of the facial nerve (cranial nerve VII).
This ganglion receives its parasympathetic preganglionic root by way of the pterygoid canal, which opens onto the posterior wall of the fossa. The preganglionic parasympathetic fibers synapse with postganglionic parasympathetic cell bodies within the ganglion. Postsynaptic parasympathetic fibers leave the ganglion and distribute with branches of the maxillary division of cranial nerve V. These fibers are secretomotor in function. They provide parasympathetic flow to the lacrimal gland and mucosal glands of the nasal fossa, palate, and pharynx.




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BONES OF SKULL / OSTEOLOGY OF FACE





Human skull

The skull  is divided into the cranium (all the skull bones except the mandible) and the mandible (or jawbone). One feature that distinguishes mammals and non-mammals is that there are also three ear bones (called ossicles):
  •        malleus (hammer)
  • —       incus (anvil)
  •                             stapes (stirrup)


Maxilla


  à  is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible, which is also a fusion of two halves at the mental symphysis.
Function
The alveolar process of the maxilla holds the upper teeth, and is referred to as the maxillary arch. The maxilla attaches laterally to the zygomatic bones (cheek bones).
The maxilla assists in forming the boundaries of three cavities:
—   the roof of the mouth
—   the floor and lateral wall of the nasal antrum
—   the floor of the orbit
The maxilla also enters into the formation of two fossae: the infratemporal and pterygopalatine, and two fissures, the inferior orbital and pterygomaxillary


Mandible
A.)  Body 
  a.)  Symphysis menti
  b.)  Mental protuberance
  c.)  Mental foramen
  d.)  Mylohyoid line
B.)  Ramus
  a.)  Mandibular foramen
  b.)  Mylohyoid groove
  c.)  Mandibular canal
  d.)  Angle
  e.)  Coronoid process
  f.)  Condyloid process
  g.)  Mandibular notch
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